1. Field Of The Invention
This invention relates to apparatus for controlling the operation of work stations in apparatus such as electrophotographic copying apparatus.
2. Description Of The Prior Art
In a common form of electrophotographic copying apparatus, an electrical image of an information medium such as a document is formed on an electrophotosensitive member in response to image-wise actinic radiation from the medium. The electrophotosensitive member includes a photoconductive layer with a conductive backing, and is transported along an endless path relative to a plurality of work stations, each of which is operative when actuated to perform a work operation on the electrophotosensitive medium. Such stations include a charging station at which a uniform charge is placed on the photoconductive layer, an exposure station at which the charged photoconductive layer is image-wise exposed to actinic radiation from the medium to create an electrostatic image of the medium in the photoconductive layer, a developing station at which the electrostatic image is contacted with finely divided charged toner particles for adhering to the photoconductive layer in a configuration defined by the electrostatic image, a transfer station at which such toner particles are transferred in the image configuration to a receiving surface, and a cleaning station at which residual toner is removed from the photoconductive layer so that it can be reused.
In applications in which the electrophotosensitive medium is continually reused, it can be constructed in a form of a drum, a plate or an endless web. The endless web configuration has certain advantages and disadvantages over drums and plates. Among the advantages is the fact that such a web can be disposed in flat configuration at one location in the apparatus to facilitate some operations such as, e.g., exposure and in curved configurations at other locations to facilitate other operations such as separation of a transfer sheet therefrom. Moreover, with web configurations more than one image may be in process at any given time. Among the disadvantages is the increased complexity of the system resulting from a need to sequentially actuate work stations in timed relation to web movement when a number of copies are being made.